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Insertion: To the bases of the 2nd and 3rd metacarpals.
• Opponens pollicis
Actions: Extension and abduction of the wrist.
Origin: From the flexor retinaculum and adjacent carpal bones.
Nerve supply: Radial nerve.
Insertion: To the shaft of the 1st metacarpal.
• Extensor digitorum Nerve supply: Median nerve.
Origin: From the common extensor origin on the lateral epicondyle of Action: Produces opposition of the thumb.
the humerus. Nerve supply: Median nerve.
Insertion: To the bases of the middle and distal phalanges of the four • Adductor pollicis
fingers via the extensor expansion. Origin: Oblique head from the bases of metacarpals; transverse head
Actions: Extension of the fingers and of the wrist (but see also the lum- from the shaft of the 3rd metacarpal.
bricals and interossei). Insertion: To the base of the medial side of the proximal phalanx of the
Nerve supply: Radial (posterior interosseous) nerve. thumb. The tendon contains a sesamoid bone.
• Extensor digiti minimi Action: Adduction of the thumb.
Origin: From the common extensor origin. Nerve supply: Deep branch of the ulnar nerve.
Insertion: To the extensor expansion of the little finger. • Abductor digiti minimi
Action: Extension of the little finger. Origin: From the pisiform bone.
Nerve supply: Radial (posterior interosseous) nerve. Insertion: To the base of the proximal phalanx of the little finger.
• Extensor carpi ulnaris Action: Abduction of the little finger.
Origin: From the common extensor origin and from the posterior bor- Nerve supply: Ulnar nerve.
der of the ulna. • Flexor digiti minimi
Insertion: To the base of the 5th metacarpal. Origin: From the flexor retinaculum and adjacent carpal bone.
Actions: Extension and adduction of the wrist. Insertion: To the base of the proximal phalanx of the little finger.
Nerve supply: Radial (posterior interosseous) nerve. Action: Flexes the proximal phalanx of the little finger.
• Supinator Nerve supply: Ulnar nerve.
Origin: From the lateral side of the humerus and the ulna. • Opponens digiti minimi
Insertion: It wraps around the radius from behind to be inserted into the Origin: From the flexor retinaculum and adjacent carpal bones.
upper part of its shaft. Insertion: To the shaft of the fifth metacarpal.
Action: Supination. Action: Opposition of the little finger.
Nerve supply: Radial (posterior interosseous) nerve. Nerve supply: Ulnar nerve.
• Abductor pollicis longus • The lumbrical muscles
Origin: From the posterior surfaces of the radius and ulna. Origins: The four muscles arise from the sides of the tendons of the
Insertion: To the base of the 1st metacarpal. flexor digitorum profundus.
Actions: Abduction and extension of the thumb. Insertions: To the lateral sides of the dorsal extensor expansions of the
Nerve supply: Radial (posterior interosseous) nerve. extensor digitorum tendon.
• Extensor pollicis brevis Actions: Flexion of the metacarpophalangeal joints and extension of
Origin: From the back of the radius. the interphalangeal joints.
Insertion: To the base of the proximal phalanx of the thumb. Nerve supply: Medial two muscles by the ulnar nerve and lateral two by
Action: Extension of the proximal phalanx of the thumb. the median nerve.
Nerve supply: Radial (posterior interosseous) nerve. • The interossei
• Extensor pollicis longus Origins: Dorsal from adjacent sides of four metacarpals and palmar
Origin: From the back of the ulna. from one side of each metacarpal.
Insertion: Into the base of the distal phalanx of the thumb. Insertions: Both dorsal and palmar are inserted into the sides of the
Actions: Extension of all the joints of the thumb. proximal phalanges and the dorsal extensor expansions in such a way
Nerve supply: Radial (posterior interosseous) nerve. that the dorsal interossei abduct the fingers and the palmar adduct them
• Extensor indicis (Fig. 39.2).
Origin: From the back of the ulna. Actions: Adduction and abduction as above. Both sets of muscles pro-
Insertion: To the side of the extensor digitorum tendon to the index duce flexion of the metacarpophalangeal joints and extension of the
finger. interphalangeal joints, as in the ‘precision grip’.
Action: Helps to extend the index finger. Nerve supply: All by the deep branch of the ulnar nerve.
Nerve supply: Radial (posterior interosseous) nerve.
• Abductor pollicis brevis The lower limb
Origin: From the flexor retinaculum and adjacent carpal bones. • Gluteus maximus
Insertion: To the base of the proximal phalanx of the thumb. Origin: From the posterior part of the gluteal surface of the ilium, the
Action: Abduction of the thumb. back of the sacrum and its associated ligaments.
Nerve supply: Median nerve. Insertion: To the gluteal tuberosity of the femur (25%) and the ilio-
• Flexor pollicis brevis tibial tract (75%).
Origin: From the flexor retinaculum and adjacent carpal bones. Actions: Extension and lateral rotation of the thigh.
Insertion: To the base of the proximal phalanx of the thumb. Its tendon Nerve supply: Inferior gluteal nerve.
contains a sesamoid bone. • Gluteus medius
Action: Flexion of the proximal phalanx of the thumb. Origin: From the gluteal surface of the ilium.
164 Muscle index